These days, as air pollution becomes severe, many hazardous substances and pollutant dust, which are harmful to the human body, are contained in air. When air containing such hazardous substances and pollutant dust, harmful to the human body, is ingested without any filtration, it will have various adverse effects on the human body. For this reason, air cleaners having various types of filter systems for filtering the hazardous substances and pollutant dust are used.
The filter system of the air cleaners according to the prior art generally comprise a pretreatment filter, a medium filter, a deodorizing filter, a HEPA (High Efficiency Particulate Air) filter and a blower fan. Generally, microorganisms harmful to the human body have a size of a few microns, and such microorganisms are removed through the HEPA filter in the filter system.
This HEPA filter is a kind of filtration media and can be made of, for example, polypropylene fiber, which is a special charged fiber. The HEPA filter is mounted in the air cleaner to filter even fine hazardous substances and pollutant dust. Also, the HEPA filter has a strong adsorption capability to completely remove house hazardous substances such as dust, mites, viruses and fungi, which are contained in air and are harmful to the human body, and pollutant particulate matter having a size of about 0.3 microns, which is very harmful to the human body, at a high removal rate of 99.9%. Thus, it serves to purify polluted air to a significantly clean state.
FIG. 1 shows a HEPA filter according to the prior art. As shown in FIG. 1, the prior filter system has a structure in which a filtering media including the HEPA filter is mounted in a case 110 formed of a plastic material.
Although prior microporous filters such as HEPA filters have excellent performance in removing microorganisms suspended in air, including general bacteria, microorganisms, which are not removed or filtered through the prior filters, still exist. Meanwhile, in the case of such types of filters, microorganisms filtered through a filter media sometimes remain on the surface of the filtration media. As a result, these microorganisms continue to grow without being discharged with purified air, so that these microorganisms cause odors when the filter is used for a long period of time. Thus, these microorganisms act as the cause of secondary contamination, which reduces the air purification performance of the filter.
In an attempt to solve the above problem, there is a method in which a separate antibacterial filter is placed in the front or rear of the HEPA filter. However, this method has problems in that an increase in the number of filter media causes pressure loss and leads to an increase in production cost. In another attempt, there is a method in which the surface of the HEPA filter is coated with antibacterial substances, but this method has a disadvantage in that the dust collection efficiency of the filter is reduced.